Data Storage Devices (DSDs) are often used to record data onto or to reproduce data from a storage media. One type of storage media includes a rotating magnetic disk where a magnetic head of the DSD can read and write data in tracks on a surface of the disk, such as in a Hard Disk Drive (HDD).
Shingled Magnetic Recording (SMR) has recently been introduced as a way of increasing the number of Tracks Per Inch (TPI) by making the tracks narrower. SMR increases TPI by using a relatively wide shingle write head with a stronger magnetic field to overlap tracks like roof shingles. The non-overlapping portion then serves as a narrow track that can be read by a narrower read head.
Although a higher number of TPI is possible with SMR, the overlap in tracks can create a problem when writing data since new writes to a previously overlapped track affects data written in the overlapping track. For this reason, tracks are usually sequentially written to avoid affecting previously written data.
In addition, sequential writing ordinarily mitigates the effects of Adjacent Track Interference (ATI) and Wide Area Track Erasure (WATER) by reducing the number of times that a particular portion of the disk may be repeatedly written. With ATI and WATER, repeated writes to the same area on the disk can interfere with or erase data written in one or more adjacent tracks. ATI and WATER can be especially problematic for SMR due to the stronger magnetic field of the write head and closer proximity of the tracks.